Optics: measuring and testing – Optical pyrometers – Plural color responsive
Patent
1987-02-04
1988-12-13
McGraw, Vincent P.
Optics: measuring and testing
Optical pyrometers
Plural color responsive
356308, 356315, 356328, G01J 558, G01J 306, G01J 332
Patent
active
047906529
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and an apparatus for determining parameters, especially pressure, temperature, concentration, number of particles and particle size distribution, of gaseous substances present in combustion processes and other high temperature processes, in which method light transmitted through or reflected or emitted by the gases is spectrally divided, and the spectral distribution of the light in the studied wavelength range is recorded a large number of times.
The rise in raw material prices and the increasing insistence on efficient measures against pollution have intensified the interest in, for example, combustion control. An American study from the middle of the 1970's shows for example that, if the efficiency of combustion processes could be increased by 1%, this would mean a saving of 15 million barrels of oil per annum in the USA alone. The combustion in coal-burning power plants is another example of a combustion process where an efficient control could save large sums of money. Thus, if the temperature in a coal-burning power plant becomes too high, slag products are deposited which, if it comes to the worst, may necessitate closing down the entire plant for cleaning. Furthermore, the emission of substances hostile to the environment could be reduced if some combustion processes could be controlled more efficiently, for example the incineration of refuse. If the combustion temperature becomes too high (above 1600.degree. C.) large amounts of NO are generated, which is one of the substances considered to contribute to the so-called forest kill. If, on the other hand, the temperature is too low, dioxine is formed which, is a dreaded environmental poison. Suitable control measures to maintain the temperature at an intermediate value can minimise the emission of these two dangerous substances.
However, to be able to conveniently control the above-mentioned and other processes, transducers are required by which the control parameters, such as the temperature, the concentration of specific substances etc., can be determined.
Unfortunately, the technical progress in this field has not kept pace with the rise in raw material prices and the environmental issues. One reason is, of course, the high temperatures which render the use of conventional transducers and measuring instruments impossible. Another reason is that the measuring environment in, for example, a coal-burning power plant places high demands on the measuring equipment which must be unsusceptible to dirt, vibrations etc. A third reason is the turbulent character of the measuring environment, i.e. the measuring conditions are subject to strong variations in time, which makes it difficult to design a measuring equipment capable of operating with great accuracy and reliabilty, and up to a few years ago only unreliable methods were available for determining temperature, concentration and other parameters. For example, the temperature was measured by means of thermocouples which interfered with the processes and therefore did not give reliable results. Furthermore, the concentration of the substances present during combustion was recorded by exhausting gas from the combustion zone and injecting it into, for example, a mass spectrometer. Also these concentration measurements were unreliable because exhausting of the sample interfered with the processes, the exhausted gas sample was cooled in the mass spectrometer, and there was a risk that the substances could interreact in the mass spectrometer so that the substances measured were different from those which were present during the process.
When it is desired, in other technical applications, to prevent the measurement from interfering with the process, use is frequently made of optical measuring techniques. One group of optical measuring techniques is based on the principle of developing by means of light a secondary effect, for example fluorescence, which carries information about the required parameter and the intensity of which is measured. Examples of such technique
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Albrechcinski et al., "Rapid-Scan Instrumentation for Spectrally & Spatially Resolved Radiance Measurements of Short-Duration Rocket Plumes", Conference ICIASF 79, Monterey, Ca., Sep. 79, pp. 57-71.
Derwent's abstract nr 03281 E/02, SU 639-320, (Irkut Univ Appld Ph), 1 Dec. 1976, (Shin Nippon Seitetsu K K), 28 May 1983.
Applied Optics and Optical Engineering, R. Kingslake, vol. V. 1969, "Grating Monochromators", p. 80.
Uneus Leif
Wallin Svante
McGraw Vincent P.
OPSIS AB
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